1. Field of the Invention
This invention relates to pyrotechnic compositions and especially such compositions which are useful in inflating an inflatable device, such as a vehicle safety restraint, as well as to methods for so inflating the device.
2. Description of the Prior Art
Various pyrotechnic formulations have been proposed for generating a gas upon combustion in order to inflate an air bag or similar safety restraint in a vehicle so as to restrain movement of an occupant in the event of a sudden deceleration of the vehicle, such as caused by a collision. In order to be employed as a pyrotechnic gas generating composition for inflatable occupant restraints, several criteria must be met. The pyrotechnic must be capable of producing non-toxic, non-flammable and essentially smokeless gases over a wide variety of temperatures and other environmental conditions. The gases that are generated must be at a sufficiently low temperature so as not to destroy the restraint or injure the occupant. The pyrotechnic must also be safe to handle and must be capable of generating a substantial amount of gas within a very short period of time, e.g., less than about 100 milliseconds.
A wide variety of pyrotechnic compositions have been suggested for possible use for inflating vehicle occupant safety restraints. Some of these compositions produce non-gaseous metal salts or oxides along with the gas that is used to inflate the restraint. Since such salts or oxides are at a considerably higher temperature than the gaseous products, following combustion of the pyrotechnic composition, e.g., about 2000.degree. F., it is necessary to retain the salts or oxides within the gas generator so as not to destroy the restraint or injure the occupant. These pyrotechnic compositions have not heretofore been considered as likely candidates for use in an occupant restraint device since elaborate filtering and/or cooling devices are required to retain the salts or oxides within the generator. This is despite the fact that such compositions produce a relatively low temperature, non-toxic gas within the requisite period of time. It would be desirable if such pyrotechnic compositions could be employed in an occupant restraint system without the need for elaborate filtering and cooling devices.